Scaffold

ABSTRACT

A scaffold comprising a relatively long and narrow platform and two upright supports for the platform which support opposite ends of the platform, each of the supports having a base structure, an upright post secured to and supported by said base structure, and a platform supporting member slidably supported on the post. One of the posts is fixedly supported by its base structure while the other post is supported for lateral movement with respect thereto parallel to the longitudinal axis of the scaffold to accommodate for changes in the horizontal distance between the lines of contact of the platform with the platform supporting member as the vertical position of one supporting member is changed with respect to that of the other. The base structure of each support has wheels projecting from one side of it. These wheels are normally out of engagement with the supporting surface but when the platform is removed from the supports, each support can be tilted to bring the wheels into rolling engagement with the supporting surface to facilitate movement of the support from one location to another. A cable and a drum with a crank are employed to raise and lower each platform supporting member with respect to its associated post. Further latch means are provided for releaseably locking each platform supporting member against downward movement in case the cable breaks or is accidently released.

Unite States EPtet Williams Dec. 3, r974 SCAFFOLD} Lowell A. Williams, Wimbledon, N. Dak. 58492 [76] Inventor:

[52] US. Cl. 182/17, l82/l46 [51] Int. Cl. E04g H18 [58] Field of Search 182/146, 145, 142, 117, 182/17, 201, 148

[56] References Cited UNITED STATES PATENTS 1 85,956 H1 877 Park 182/146 1 ,004,550 10/191 l Bcrtke l82/2'l 2,914,] 35 l l/] 959 Crouch l82/20l 3,169,604 2/l965 Pranger 182/146 3,340,960 Wilson l82/l l7 Primary Examiner-Reinaldo P. Machado Attorney, Agent, or Firm-Dorsey, Marquart, Windhorst, West & Halladay 5 7 ABSTRACT A scaffold comprising a relatively long and narrow platform and two upright supports for the platform which support opposite ends of the platform, each of the supports having a base structure, an upright post secured to and supported by said base structure. and a platform supporting member slidably supported on the post. One of the posts is fixedly supported by its base structure while the other post is supported for lateral movement with respect thereto parallel to the longitudinal axis of the scaffold to accommodate for changes in the horizontal distance between the lines of contact of the platform with the platform supporting member as the vertical position of one supporting member is changed with respect to that of the other. The base structure of each support has wheels projecting from one side of it. These wheels are normally out of engagement with the supporting surface but when the platform is removed from the supports, each support can be tilted to bring the wheels into rolling engagement with the supporting surface to facilitate movement of the support from one location to another. A cable and a drum with a crank are employed to raise and lower each platform supporting member with respect to its associated post. Further latch means are provided for releaseably locking each platform supporting member against downward movement in case the cable breaks or is accidently released.

7 Claims, 7 Drawing Figures SCAFFOLD BACKGROUND OF'THE INVENTION It is highly desirable to have a scaffold assembly which provides a relatively long working area, which is stable, which can be readily adjusted and which can be conveniently transported from one point to another. The most common type of scaffold is one which must be assembled on the job and which must be disassembled to be moved any substantial distance. Various arrangements have been made for providing a scaffold which can be moved without disassembly. These scaffolds, however, are either in the form of relatively bulky units or ones which provide a very limited work ing space. Where there is only a limited working space, it is necessary to shift the scaffold from time to time.

SUMMARY OF THE PRESENT INVENTION The present invention is concerned with a scaffold which can be readily moved, which requires a minimum of assembly work to be ready for use, which is safe, which can be readily adjusted and which is extremely stable.

Broadly, I accomplish this by providing a platform which is supported by two supports, each of which consistsvof a base structure designed to rest on the groundor other supporting surface, a post supported by the base structure and a platform member which is slidably supported by the post with means for adjusting the vertical position of the platform supporting member.

Preferably, one of the posts is secured to the base structure in a manner to prevent lateral movement of the post with respect to the base structure .while the other post is secured to the base structure in a manner to permit such lateral movement in a direction parallel to the longitudinal axis of the platform. By providing for such lateral movement, it is possible to accommodate for the changes in the horizontal distance between the lines of contact of the platform with the platform supporting members as the vertical position of one supporting member is changed with respect to that of the other.

Wheels are preferably secured to each base structure, these wheels projecting from one side of the base structure normally out of engagement with the supporting surface. Upon removal of the platform from the supports, each support can be tilted to bring the wheels into rolling engagement with the supporting surface to facilitate movement of the support from one location to another.

Means are also provided in connection with each platform supporting member to raise and lower the platform supporting member with respect to the posts. These means normally take the form ofa cable running over a pair of pulleys and secured to a drum which can be turned to raise and lower the platform supporting member. Downward movement of the platform supporting member is prevented, even if the cable breaks, by a safety latch which is biased so as to prevent downward movement of the platform supporting member. When it is desired to lower the platform supporting member, a release member is actuated.

Each base structure is provided with a plurality of foot members, certain of which are vertically adjustable to enable levelling of the base structure and consequent adjustment of the post to a vertical-position. A guy cable is also connected between the base structure and the top of the post on the opposite side of the post that from which the platform supporting member projects. This guy cable acts to hold the post in an upright position despite the bending torque applied to the posts by the weight of the occupants on the platform.

Various other features of the invention will be apparent from a consideration of the accompanying specifcation, claims and drawing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of my improved scaffold;

FIG. 2 is an end elevational view of one of the platform supports, the platform being shown in section with the section being taken along the line 22 of FIG.

FIG. 3 is a top plan view of the base structure of the support of FIG. 2 with a section being taken along the line 33 of FIG. I;

FIG. 4 is a sectional view showing the safety locking mechanism for preventing downward movement of the platform supporting member, the section being taken along the line 4-4 of FIG. 2;

FIG. 5 is a sectional view taken along the line 55 of FIG. I and showing a plan view of the other base DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, the scaffold comprises a platform member and two upright supports II and 12. Supports l1 and 12 include two base structures 13 and 14. respectively and two platform supporting members 15 and 16 respectively. They also include posts 17 and 18 on which the platform supporting members 15 and 16 are respectively mounted for vertical sliding movement with respect to the posts.

Referring first to the support 11, the post 17 of this support is rigidly secured to the base structure 13. The base structure 13, shown in plan view in FIG. 3, has four arms 20, 21, 23 and 24 which collectively radiate from a collar 25 having an opening therethrough of the same cross-sectional configuration and dimensions as those of the post 17. Thus, when the post 17 is inserted into the collar 25 it is rigidly retained therein in avertical position. The post 17 is preferably formed of a beam of square hollow cross-section so that the post 17 is relatively rigid without being excessively heavy. Secured to the ends of the arms 20, 21, 23 and 24 are posts 28, 29, and BICAI the bottom of each of these posts a base plate 32 is secured..The posts 28 and 29, as best shown in FIG. 2, are vertically adjustable by being provided with a plurality of holes 33 therethrough. At the end of each of the arms 20, 21, 23 and V 24 there is a sleeve through which the post extends. In the case of arms 20 and 21, this sleeve has an aperture 34 therethrough and any of the holes 33 can be brought into alignment with this aperture 34. A bolt or any other suitable fastening means is passed through the aperture 34 and the selected one of the apertures 33. By selection of the aperture 33, the vertical position of the post can be adjusted and hence the position of arms 20 and 21 with respect to the base plates 32. In the case of posts 30 and 31, these posts are not vertically adjustable but can be rotated either to the position shown or to a-position 180 displaced therefrom in which position the base plates 32 are directly inwardly. The posts 30 and 31 are provided at the upper ends thereof with handles 38 for angular rotation of the posts. Even though posts 30 and 31 are not adjustable vertically, the position of the standcan be adjusted by adjustment of posts 28 and 29 to cause the post 17 to be in a vertical position regardless of the supporting surface on which the base plates 32 rest.

The base structure 13 is further provided with two wheels 36 which are journaled in brackets 37 projecting forwardly from the arms 23 and 24 respectively. The purpose of these wheels are to enable ready movement of the support 11 when the platform is removed therefrom. Under these conditions, after the front base plates 32 have been rotated through an angle of l80 from that shown so that the major portions thereof are retracted beneath the base structure rather than underlying the wheels 36 as shown, it is possible by tipping the entire support backwardly (in a counterclockwise direction as viewed in FIG. 2) to bring the wheels 36 into engagement with the ground. At this point, the posts 17 will be closer to a horizontal position than to a vertical position. The entire support 11 can then be readily rolled on the wheels 36 to a desired new location. As will be presently explained, the other support 12 is similarly provided with wheels for facilitating its movement.

Referring now to the other support member 12, this support member is somewhat different than support member 11 in that it permits lateral movement of the I post 18 supported by it in a'direction parallel to the longitudinal axis of platform 10. In the case of this support, the base structure comprises two side beams 41 and 42 which have welded therebetween a rectangular frame member 43. As best shown in FIGS. 5 and 6, there are two channel shaped members 47 and 48 rigidly secured to the transversely extending members of frame 43. A post support platform 49 is provided with two pairs of rollers 50 and 51 which roll within the channels of channel shaped members 47 and 48. By reason of these rollers 50 and 51 rolling within the channels 47 and 48, it will be readily apparent that platform 49 can move transversely of the base structure 14 to any desired position. The moveable platform 49 of base structure 14 is provided with a socket 54 of the same cross-sectional configuration and dimensions as the post 18 so that the post 18 can be inserted into the socket 54 and firmly secured thereto for limited lateral movement with respect to the rest of base structure 14.

Secured to opposite ends of the side beams 41 and 42 are a plurality of posts 58 and 59 corresponding to posts'28, 29, and 31 of base structure 13. The posts all have base plates 32 secured at their lower end. The posts 58 supported at the rear ends of side beams 41 and 42 are vertically adjustable in the same manner as posts 28 and 29. The posts 59 secured at the front of the side beams 41 and 42 have handles 38 secured thereto for angularlyturning the posts 59 and the base plates 32 secured thereto from the position shown to a position 180 displaced therefrom.

As with base structure 13, a pair of wheels 36 are mounted at the front of the base structure. These wheels are secured to brackets 62 which are rigidly secured to the front wall of the rectangular frame 43.

Each of the supports 11 and 12 have a guy cable 64 extending from the base structure to the top of the post. The lower end of each of these cables is secured to a bracket 65 rigid with the base structure and extending rearward therefrom. The upper end of each cable is provided with a hook which hooks into the upper end of the post associated with that base structure. This guy cable resists any tendency of the posts 17 and 18 to bow in the direction of the platform 10 as the weight of the workers is placed upon the platform.

As previously indicated, the platform supporting members 15 and 16 are mounted for vertical sliding movement with respect to their associated posts 17 and 18. Each of these members comprises a horizontal beam 68 having at its inner end a yoke 69 secured thereto. Journaled between the two arms of the yoke 69 are rollers 70 and 71 which are spaced apart a distance equal to the width of the post 17. Thus the rollers 70 and 71, which as best shown in FIG. 1, may be curved inwardly straddle the post 17 and firmly engage the opposite sides thereof. A second parallel yoke 73 is spaced from yoke 69 and is secured to an angular beam 74 rigidly attached to the horizontal beam 68. This second yoke 73 again has tworollers 76 and 77 journaled between the arms of the yoke and straddling the post 17. The rollers 70, 71, 76 and 77 thus engage the opposite sides of post 17 at vertically spaced points so as to hold the platform 68 at right angles to the post 17 while readily permitting sliding movement of the platform supporting member 15 in a vertical direction with respect to post 17.

The platform supporting member 16 is of similar construction to platform supporting member 15, as clearly shown in FIG. 6. The same reference characters have been applied to the corresponding elements of this platform and it is believed that the construction of platform supporting member l6 will be obvious from a comparison of the reference numerals referred to in describing platform supporting member 15. Thus, the platform members 15 and 16 are secured to posts 17 and 18 in such a manner that they are readily adjustable in a vertical direction. As will be presently explained, each platform supporting member has its own adjusting means. The reason for this is that the platform 10 is relatively long and it would be obviously impossible for a worker to adjust both platforms simultaneously. Where two workers are working on a scaffold, each worker may independently raise and lower his end of the scaffold until the scaffold is in the desired vertical position and lies in a generally horizontal plane. The means for adjusting the vertical position of platform supporting member is the same with both platform supporting' members and this means will be described in detail in connection with platform supporting member 15 shown in FIG. 2.

In the case of each of the platform supporting members 15 and 16, there is a vertical post 80 which is secured at its lower ends between the yokes 69 and 73. This post 80 is in the form of a hollow beam which is square in cross section. Secured at the upper end of each post 80 is a winch 81 having a handle 82. The winch 81 is of conventional construction and has a drum designed to have a cable wound thereon. Suitable dog and ratchet means are provided for maintaining the cable in any adjusted position. A dog release 83 is provided for releasing the dog to permit unwinding of the cable. Such winches are of conventional construction and the details thereof are not shown in the drawing. Wound on each winch 81 is a cable 85 which has one end secured to the drum of the winch. The cable passes over a pulley 86 secured to the vertical post 80. The

. cable then passes upwardly over a second pulley 87 secured to the upper end of the main post 17. The cable then passes downwardly and is secured at its opposite end to a bracket 88 secured to the post 80 of the platform supporting member (best shown in FIG. 6). It will be obvious that as the drum of the winch 81 is rotated in a counterclockwise direction (as viewed in FIG. 2), the platform supporting member will be raised with respect to the associated post of the main support. Thus, referring specifically to FIG. 2, as the drum of the winch 81 is rotated in a counterclockwise direction, the post 80 of the platform supporting member is raised to raise the platform supporting member. If it is desired to lower the platform supporting member 15, the dog release 83 is released and the drum of the winch 81 is allowed to run in a clockwise direction to lower the post 80 and hence the platform supporting member 15.

As an additional safety measure, I provide a safety latch 90. This safety latch comprises a tiltable plate 91 having an enlarged portion 92 with an aperture 93 therein, as best shown in FIG. 4. The aperture 93 is designed to surround (referring to FIG. 2) the posts 17. The aperture 93 is basically of the same cross-sectional area and configuration as that of the post 17. The plate 91 has a relatively narrow tongue portion 92 which extends through the post 80 of platform supporting member 15. As best shown in FIG. 2, the post 80 has a relatively narrow slot 95, the walls of which act as a fulcrum for the plate 91. The opposite wall of the post 80 has a relatively wide opening 96 to permit rocking movement of the tongue 92 about the fulcum provided by the slot 95. A spring 97 located within the post 80 engages at its upper end a stop (not shown). At its lower end, it engages the tongue 92 of the plate 91 to bias the plate in a clockwise direction (as shown in FIG. 2). When so biased, the inner and outer walls of the opening 93 of plate 91 engage and tend to bite into the post 17. It will be seen that any weight exerted upon the platform 19 tends to accentuate this tendency of the plate 91 to be rotated in a clockwise direction into binding engagement with the post 17. Thus, the safety latch 90 just described tends to maintain the platform against downward movement from any vertically adjusted position. The purpose of this is to insure that if the winch should accidentally be released or if the cable 85 should break, the platform 15 will not drop downwardly along the post 17.

It is, of course, necessary to provide some means for I releasing the safety latch 90 in order to permit downward movement of the platform 15 when it is desired. This means takes the form of a rod 98 having a knob 99 at the upper end thereof to act as a handle. The rod 98 is suitably supported for sliding movement and is pivotally secured at its lower end to the latch plate 91 I by extending through an aperture 100 therein (see FIG. 4). When it is desired to release the safety latch 90, all that it is necessary to do is to pull upwardly on the knob 99. This will rock the plate 91 in a counterclockwise direction about the pivot provided by the slot 95. Such rocking action is taken against the force exerted by spring 97 and the force exerted by the weight on platform 19. When the plate 91 is so rocked, it is released from the post 17 and it is possible by turning the drum of the winch 81 in a clockwise direction, as previously described, to lower the platform supporting member 15.

The means for raising and lowering the platform supporting member 16 is identical to that described in connection with platform 15 and it is not believed necessary to repeat this description in connection with platform 16. Reference characters have been applied to certain key elements of the means for raising and lowering the platform 16, these reference characters being identical to those employed in connection with the mechanism for raising and lowering the platform supporting member 15. In view of the similarity of the reference characters and the similarity of the structures involved, it is believed unnecessary to repeat the description of the means for raising and lowering the platform 16.

The platform 10 comprises a horizontal panel 110 which may be reinforced, if desired, by vertical pipes and girder pipes 106 welded together and secured underneath the panel 110. The panel 110 has pipes 112 secured underneath each end and extending beyond the panel. Each beam 68 has U-shaped brackets 118 secured thereto as by welding. These brackets are spaced so as to support the projecting portions of pipes 112 and hold the top of the panel 110 substantially flush with the tops of beams 68, as shown in detail in FIG. 7. By reason of this pipe and bracket connection, the platform can pivotally move with respect to the platform support as the latter is moved up and down.

Secured to the panel member 110 by any suitable means are a plurality of vertical posts 113 which have secured to the tops thereof a horizontal rail member 114. Spaced horizontal planks 115 and 116 are secured to the posts 113 to form protective rails to minimize the tendency of articles, such as paint buckets, placed on the panel 110 to be accidentally shoved off of the platform 10. As shown, the lower edge of plank 115 is in contact with the panel 110 with the upper plank 116 at an intermediate height. The posts 113, the railing 114,

and the planks 115 and 116 function to provide protec tion for the occupants of the platform 10 to prevent their falling off of the platform. It is, of course, understood that the front of the panel 110 will be close to the surface being worked upon so that there is no likelihood of people falling off of that side of the panel 110.

In setting up the scaffold, the base plates .32 of both base structures 13 and 14 are rotated to a position displaced with respect to that shown. In this position, if either platform is tipped backwardly so that the forward posts (28 and 29 of base structure 13 or 58 of base structure 14) are up in the air, the wheels 36 can be brought into engagement with the ground or other supporting surface. Under these conditions, the posts 17 or 18 of the associated support is in an inclined position where the upper end of the post can be readily manipulated by the operator. The support is then rolled to the desired position and raised upwardly until the main post thereof is substantially vertical. Each support is adjusted in position until the posts 17 and 18 are spaced approximately equally from the building wall or other surface to be worked on. The plates 32 at the back end of the supports 13 and 14 are now brought into the position shown by rotating the handles 38 at the upper end of the post to which they are attached. This can readily be done by tilting the base structures 13 and 14 upwardly slightly at their rear ends while the rear base plates 32 are being moved into the position shown. The vertical positions of the forward base plates are now adjusted by selecting the proper hole 33 through which the pin passing through aperture 34 extends. These posts are adjusted until the vertical posts 17 and 18 are in substantial vertical position. If the rear base plates 32 are not evenly engaging the ground, a shim member may be employed. With the platform supporting members 15 and 16 in their lower position, the platform is now placed on these platform supporting members and secured in position by placing the ends of pipes 112 in the brackets 118 on beams 68. At the same time, the cables 64 are secured to the upper ends of the posts 17 and 18 by engaging the hooks at their upper ends to the upper ends of posts 17 and 18.

It is now possible to raise the platform 10 to the desired position. Where there are two operators, the operators can simultaneously turn the cranks 82, keeping the two platform supporting members and 16 always at approximately the same height. Even in this case, however, it is very difficult for both operators to adjust the platform by exactly the same amount. Hence, one end or the other of the platform will temporarily be higher than the other. Since the platform 11) is fastened at both ends to the platform supporting members 15 and 16, this would result in lateral stress being placed upon the platform supporting members. As is well known, the horizontal distance between two ends of a member shortens as the member is tilted. Since the distance between the posts 17 and 18 remains fixed, a tilting of the platform panel 110 would result in a tendency for the platform supporting members 15 and 16 to be pulled together and to place stress either upon these members or upon the posts 17 and 18. This tendency is avoided by l'CflSOIl'Of the fact that post 18 is supported by the platform 49 which rolls in the frame 43 of the base structure 14. Thus, as one end or the other of the platform 10 tends to be higher than the opposite end, thus shortening the horizontal distance between the ends of the platform,-the post 18 moves towards the post 17 to accommodate this movement. Since post 17 is fixed, the platform 10 remains fixed aginst longitudinal movement even though post 18 can move toward and away from post 17.

The feature just described is particularly important when there is only one operator. Here, he must successively go from one end of the platform to the other, alternately raising each end of the platform. Under such conditions, if the operator is to avoid an excessive number of trips back and forth, alternate ends of the platform panel 110 will be substantially higher than their opposite ends until the platform is finally adjusted to the height desired.

Because of the safety latch 90, platform supporting members 15 and 16 are always held against downward movement even if the cable 85 should accidentally break or if the winch 81 should accidentally be released. Thus, the scaffolding is extremely safe.

When it is desired to move the scaffolding to a new position, it is only necessary to disconnect the fastening means 112 and remove the platform 10 from the scaffold supporting members 15 and 16. The supports 11 and 12 can then be moved on wheels 36 in the manner previously described, with the process described above being repeated when it is desired to assemble the scaffold in the new position.

While I have described the scafiold as having only one platform 10, there may be additional sections. Thus, in FIGS. 1 and 7, I have shown a second panel section in dotted lines. It will be noted that the horizontal beam 68 has brackets 118 on both sides thereof to facilitate connecting additional platforms. If additional platforms are used, it will, of course, be necessary to employ additional supports, one for each added platform. Furthermore, it is desirable that the additional supports be of the type of support 12 in which vthe post 18 can move parallel to the direction of the platform. Even though the additional upright supports will provide for longitudinal movement of the posts associated therewith, the entire platform assembly will be stationary since they are all interconnected and since the platform 10 shown in FIG. 1 is supported by support 12 which does not permit movement of the vertical post associated therewith.

CONCLUSION It will be seen that l have provided a scaffold which provides a long working surface, which is extremely safe, which can be readily moved from location to location even by one man and which permits ready adjustment of the height of the scaffold without any stress being placed upon the scaffold structure.

While I have shown a specific embodiment of my invention, it is to be understood that this is for the purposes of illustration only and that the scope of the invention is to be limited solely by the appended claims.

I claim as my invention:

1. A scaffold comprising:

a relatively long and narrow platform and first and second spaced upright supports for supporting opposite ends of said platform,

each of said supports comprising a base structure adapted to rest in stationary position upon a supporting surface, a vertical post supported by said base structure, a platform supporting member slidably supported for vertical movement on said post, and means for moving said platform supporting member vertically with respect to said post-to different selected vertical positions,

the base structure of the first of said supports having means for supporting its associated post and platform supporting member against lateral movement with respect thereto, and v v the base structure of the second of said supports hav ing means for supporting its associated post and platform supporting member for limited lateral movement with respect thereto parallel to the longitudinal axis of the scaffold to accomodate for changes in the horizontal distance between the lines of contact of said platform with said platform supporting members as the vertical position of one platform supporting member is changed with respect to that of the other. 2. The scaffold of claim 1 in which the base structure of each support has wheels projecting from one side thereof normally out of engagement with the supporting surface so that when the platform is removed from the supports, each support can be tilted to bring the wheels into rolling engagement with the supporting surface to facilitate movement of said support from one location to another.

3. The scaffold of claim 1 in which each platform supporting member has elevating means for moving said supporting member upwardly to adjust the height of the platform and releasable safety lock means independent of said elevating means for preventing downward movement of said supporting members.

4. The scaffold of claim 3 in which said releasable safety lock means is in the form of a pivoted plate having an opening therein through which the post extends and means biasing said plate to a position where it grips the post whenever said supporting member tends to move downwardly.

5. The scaffold of claim 1 in which means in the secnd of said supports for supporting the associated post for lateral movement comprises a rolling platform mounted for rolling movement on the base structure of said support in a direction parallel to the longitudinal axis of the platform.

6. The scaffold of claim 2 in which the base structure of each support has base plates secured thereto and normally engaging the supporting surface, at least one of said base plates in each base structure being moveable from a position'in which it would interfere with the engagement of the wheels with the supporting surface upon such tilting of the support to a position in which it allows such engagement. 7. A scaffold comprising: a relatively long and narrow platform and first and second spaced upright supports for supporting opposite ends of said platform, each of said supports comprising a base structure adapted to rest upon a supporting surface, a vertical post secured to and supported by said base structure, a platform supporting member slidably supported on said post, and means for moving said platform supporting member vertically with respect to said post,

the base structure of each support having wheels projecting from one side thereof and normally out of engagement with the supporting surface and base plates secured to said base structure and normally engaging the supporting surface, at least one of said base plates in each base structure being movable from a wheel underlying position, in which it would interfere with the engagement of the wheel with the supporting surface upon tilting of the support, to a retracted position in which it allows such engagement when said support is so tilted. 

1. A scaffold comprising: a relatively long and narrow platform and first and second spaced upright supports for supporting opposite ends of said platform, each of said supports comprising a base structure adapted to rest in stationary position upon a supporting surface, a vertical pOst supported by said base structure, a platform supporting member slidably supported for vertical movement on said post, and means for moving said platform supporting member vertically with respect to said post to different selected vertical positions, the base structure of the first of said supports having means for supporting its associated post and platform supporting member against lateral movement with respect thereto, and the base structure of the second of said supports having means for supporting its associated post and platform supporting member for limited lateral movement with respect thereto parallel to the longitudinal axis of the scaffold to accomodate for changes in the horizontal distance between the lines of contact of said platform with said platform supporting members as the vertical position of one platform supporting member is changed with respect to that of the other.
 2. The scaffold of claim 1 in which the base structure of each support has wheels projecting from one side thereof normally out of engagement with the supporting surface so that when the platform is removed from the supports, each support can be tilted to bring the wheels into rolling engagement with the supporting surface to facilitate movement of said support from one location to another.
 3. The scaffold of claim 1 in which each platform supporting member has elevating means for moving said supporting member upwardly to adjust the height of the platform and releasable safety lock means independent of said elevating means for preventing downward movement of said supporting members.
 4. The scaffold of claim 3 in which said releasable safety lock means is in the form of a pivoted plate having an opening therein through which the post extends and means biasing said plate to a position where it grips the post whenever said supporting member tends to move downwardly.
 5. The scaffold of claim 1 in which means in the second of said supports for supporting the associated post for lateral movement comprises a rolling platform mounted for rolling movement on the base structure of said support in a direction parallel to the longitudinal axis of the platform.
 6. The scaffold of claim 2 in which the base structure of each support has base plates secured thereto and normally engaging the supporting surface, at least one of said base plates in each base structure being moveable from a position in which it would interfere with the engagement of the wheels with the supporting surface upon such tilting of the support to a position in which it allows such engagement.
 7. A scaffold comprising: a relatively long and narrow platform and first and second spaced upright supports for supporting opposite ends of said platform, each of said supports comprising a base structure adapted to rest upon a supporting surface, a vertical post secured to and supported by said base structure, a platform supporting member slidably supported on said post, and means for moving said platform supporting member vertically with respect to said post, the base structure of each support having wheels projecting from one side thereof and normally out of engagement with the supporting surface and base plates secured to said base structure and normally engaging the supporting surface, at least one of said base plates in each base structure being movable from a wheel underlying position, in which it would interfere with the engagement of the wheel with the supporting surface upon tilting of the support, to a retracted position in which it allows such engagement when said support is so tilted. 